JP3379745B2 - Transparent conductive oxide material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double oxide material having excellent visible light transmission property and good electrical conductivity, and such a material is a liquid crystal device ( It is applied to transparent electrodes such as LCDs and solar cells, antistatic films, electromagnetic shielding films, anti-fog glass and heat ray reflective glass.

[0002]

2. Description of the Related Art At present, transparent conductive materials include transparent electrodes for liquid crystal devices (LCD) and solar cells, electromagnetic shielding films, antistatic films, anti-fog glass,
It is used for heat ray reflective glass, etc. Among them, indium oxide-based and tin oxide-based materials have relatively high electrical conductivity and also have visible light transmission to some extent, so they are widely used for the above applications. There is.

In applying the above-mentioned materials, these materials are formed by a physical film forming method such as a sputtering method or an ion plating method, or a chemical film forming method such as a sol-gel method or a spray pyrolysis method. Has been used.

Here, for transparent electrodes for liquid crystal devices (LCDs) and solar cells, the market of which is expanding significantly in recent years, the electrical conductivity is sufficiently high and the patterning property by etching is relatively easy. Therefore, ITO (Indium) obtained by adding tin of several mol% to indium oxide is used.
-Tin-Oxide) is mainly used.

However, while ITO is superior in conductivity to other conventional materials, it is not transparent.
Visible light transmission is not high due to the intrinsic characteristics of the material,
In particular, it has a drawback that it absorbs a large amount of visible light in a short wavelength range, and a thin film after film formation looks a little bluish. Also IT
Since the fundamental absorption edge of O is around 370 nm, it hardly transmits bright light in the ultraviolet region and is disadvantageous in terms of energy efficiency when applied to an electrode material such as a solar cell.

On the other hand, indium oxide, which is the main constituent of ITO, has a poor resource property and is quite expensive at present, so that the film forming cost is also a problem. Other,
Since indium oxide is difficult to sinter, it is not easy to manufacture a high-density target by a sputtering method which is a typical film forming method.

[0007]

In view of the above problems, the present inventor has made diligent studies and, as a result, found that the general formula: M _2-x Sb ₂
O ₇ [M = Zn, -0.2≤x≤0.2] is a complex oxide having a pyrochlore type crystal structure, and is a group III metal element In or G containing a lanthanoid element.
By doping at least one selected from a, Al, Y, La, Nd, Sm, Eu, Gd, and Yb, a transparent conductive oxide material having a novel composition was found and the present invention was achieved.

That is, the present invention is based on Zn _2-x Sb ₂ O ₇
A transparent conductive oxide material characterized by being a complex oxide having a pyrochlore type crystal structure represented by [−0.2 ≦ x ≦ 0.2], wherein a Zn site contains a lanthanoid element III In, Ga, Al, Y, L which are group metal elements
a complex oxide having a pyrochlore type crystal structure doped with at least one selected from a, Nd, Sm, Eu, Gd, and Yb at a ratio of 0.01 to 20 atomic%, and oxygen vacancies are generated by reducing atmosphere annealing. The present invention provides a transparent conductive oxide material which is a double oxide having a pyrochlore type crystal structure in which carrier electrons are injected.

In the present invention, it is important that the molar ratio of Zn and Sb is 2-x: 2 [-0.2≤x≤0.2]. The composite oxide having a pyrochlore type crystal structure formed of the above constituent elements has a wider bandgap than ITO, and its basic absorption edge is located near the ultraviolet. For this reason,
Less absorption of visible light in the short wavelength range than ITO,
Excellent transmittance up to near UV can be expected. In addition, the pyrochlore type crystal structure is a cubic system and has high crystal symmetry, so that in the polycrystalline state, the contribution of the crystal orientation to the movement of carrier electrons is small, and the resistance of the grain boundary is low, resulting in high electrical conductivity. You can expect a degree. However, if the composition ratio is out of the above range, a second phase other than the pyrochlore phase exhibiting high electric conductivity may be generated after firing, and the electric conductivity may decrease.

Next, in order to obtain a double oxide of the present invention having a high density of 80% or more in relative density and a uniform composition,
500-
It is calcined at 1000 ° C., and is further sintered in the temperature range of 700 to 1400 ° C. in the atmosphere. Mixing is preferably performed with a wet ball mill, and when the temperature is out of the sintering temperature range, the pyrochlore phase is not sufficiently formed, or the second phase other than the pyrochlore phase is generated, which is not preferable.

By doping the Zn ²⁺ site having the above composition with a group III metal element containing a lanthanoid element, carrier electron injection resulting from charge compensation by substitution of a high-valence element is also possible. Group III metal elements including lanthanoid elements used in the present invention are In, G
a, Al, Y, La, Nd, Sm, Eu, Gd, and Yb. Carrier injection electrons are possible by doping with at least one additive element selected from these, and further, electric conductivity A material with improved

In this case, the doping amount of the additional element is In,
Ga, Al, Y, La, Nd, Sm, Eu, Gd, Yb
It is desirable to dope at least one additive element selected from metals or their oxides in a proportion of 0.01 to 20 atomic%. If the content exceeds this range, the additive element exceeds the solid solubility limit, and as a result, a second phase other than the pyrochlore phase is generated, which may lead to a decrease in electrical conductivity. Therefore, it is desirable that the doping amount of the additional element is within the above range.

Further, it is also possible to inject carriers resulting from charge compensation by generating oxygen vacancies by reducing and annealing the complex oxide having the above composition. After baking the composite oxide having the above composition in the air, it is heated at 300 ° C. to 120 ° C. in a reducing atmosphere.
It is suitable to anneal in the temperature range of 0 ° C. for 1 to 60 hours. The oxygen partial pressure at this time is 10 ⁻³ to 10 ⁻²¹ atm.
And is performed by treatment in nitrogen or a mixed gas of nitrogen and hydrogen.

On the other hand, the main constituent elements of the complex oxide of the present invention are Sb and Zn, and Sb and Zn are very inexpensive as compared with expensive In, which is the main constituent element of ITO. Therefore, the double oxide material of the present invention can be manufactured at a lower cost than ITO. Furthermore, antimony oxide is highly reactive with cadmium oxide or zinc oxide,
Therefore, it is possible to sinter at a low temperature, and the sinterability is good. Therefore, there is an advantage that a high-density sputtering target which is a film forming material can be easily manufactured.

[0015]

EXAMPLES The present invention will be further described below based on examples, but the invention is not limited to these examples.

Example 1 Cadmium oxide powder (CdO) and antimony oxide powder (Sb ₂ O ₅ ) having an average particle size of 1 μm or less and a purity of 99.99%.
Was weighed to a molar ratio of 2: 1 and wet-mill mill mixed in an ethanol solvent. Furthermore, after drying the obtained slurry at 60 ° C. for 24 hours, 700 ° C. in an alumina crucible.
It was calcined at ℃ for 5 hours. The precursor after calcination was wet-ball milled again in an ethanol solvent, dried, and then 2% by weight of PVA was added as a molding binder.

After that, the particle size was adjusted to 150 μm under and 1
After uniaxial molding with a size of 5 mmφ × 3 mmt and rubber pressing (2 t / cm ² ), the molded green disk was fired at 1200 ° C. for 5 hours in the air.

The sintered body prepared as described above had a brown color, and as a result of an analysis by a powder X-ray diffraction method, only a pyrochlore phase was recognized and it was assigned to Cd ₂ Sb ₂ O ₇ .

Example 2 A zinc oxide powder (ZnO) having an average particle size of 1 μm or less and a purity of 99.99% and an antimony oxide powder (Sb ₂ O ₅ ) were weighed out in a molar ratio of 2: 1 and an ethanol solvent was used. Wet ball mill mixing in. Further, the obtained slurry is added to 6
After drying at 0 ° C for 24 hours, 700 ° C in an alumina crucible,
It was calcined for 5 hours. The precursor after calcination was wet-ball milled again in an ethanol solvent, dried, and then 2% by weight of PVA was added as a molding binder.

Then, the particles were sized to 150 μm under,
After uniaxial molding with a size of 5 mmφ × 3 mmt and rubber pressing (2 t / cm ² ), the molded green disk was fired at 1200 ° C. for 5 hours in the air.

The sintered body prepared as described above had a brown color, and as a result of analysis by the powder X-ray diffraction method, only a pyrochlore phase was recognized and it was assigned to Zn ₂ Sb ₂ O ₇ .

Example 3 Cadmium oxide powder (CdO) and antimony oxide powder (Sb ₂ O ₅ ) having an average particle size of 1 μm or less and a purity of 99.99%.
And indium oxide powder (In ₂ O ₃ ) were weighed so that the molar ratio was 1.8: 1: 0.1, and wet-ball mill mixed in an ethanol solvent. Further, the obtained slurry was dried at 60 ° C. for 24 hours and then dried in an alumina crucible.
It was calcined at 00 ° C for 5 hours. The precursor after calcination was wet-ball milled again in an ethanol solvent, dried, and then 2% by weight of PVA was added as a molding binder.

Then, the particles are sized to 150 μm under,
After uniaxial molding with a size of 5 mmφ × 3 mmt and rubber pressing (2 t / cm ² ), the molded green disk was fired at 1200 ° C. for 5 hours in the air.

The sintered body prepared as described above had a gray color, and as a result of analysis by a powder X-ray diffraction method, only a pyrochlore phase was recognized and it was assigned to Cd ₂ Sb ₂ O ₇ . Furthermore, the peak of the indium oxide phase was not recognized, and a shift was recognized as compared with the peak of Cd ₂ Sb ₂ O ₇ without addition.
It is determined to have replaced solid solution d ₂ Sb ₂ O _7.

Example 4 Cadmium oxide powder (CdO) and antimony oxide powder (Sb ₂ O ₅ ) having an average particle size of 1 μm or less and a purity of 99.99%.
And ytterbium oxide powder (Yb ₂ O ₃ ) was weighed so that the molar ratio was 1.8: 1: 0.1, and wet-ball mill mixed in an ethanol solvent. Further, the obtained slurry was dried at 60 ° C. for 24 hours and then calcined in an alumina crucible at 700 ° C. for 5 hours. The precursor after calcination was wet-ball milled again in an ethanol solvent, dried, and then 2% by weight of PVA was added as a molding binder.

After that, the particles were sized to 150 μm under and 1
After uniaxial molding with a size of 5 mmφ × 3 mmt and rubber pressing (2 t / cm ² ), the molded green disk was fired at 1200 ° C. for 5 hours in the air.

The sintered body prepared as described above had a pale green color, and as a result of analysis by a powder X-ray diffraction method, only a pyrochlore phase was recognized and it was assigned to Cd ₂ Sb ₂ O ₇ .

Further, no peak of the ytterbium oxide phase was observed, and a shift was observed in comparison with the peak of Cd ₂ Sb ₂ O ₇ without addition. Therefore, the added ytterbium oxide was replaced with Cd ₂ Sb ₂ O ₇ . It was determined that a solid solution was formed.

Example 5 Cadmium oxide powder (CdO) and antimony oxide powder (Sb ₂ O ₅ ) having an average particle size of 1 μm or less and a purity of 99.99%
Was weighed to a molar ratio of 2: 1 and wet-mill mill mixed in an ethanol solvent. Furthermore, after drying the obtained slurry at 60 ° C. for 24 hours, 700 ° C. in an alumina crucible.
It was calcined at ℃ for 5 hours. The precursor after calcination was wet-ball milled again in an ethanol solvent, dried, and then 2% by weight of PVA was added as a molding binder.

Then, the particles are sized to 150 μm under,
After uniaxial molding with a size of 5 mmφ × 3 mmt and rubber pressing (2 t / cm ² ), the molded green disk was fired at 1200 ° C. for 5 hours in the air. Further, the sintered body was annealed in a nitrogen stream at 1000 ° C. for 10 hours in a reducing atmosphere.

The sintered body prepared as described above had a gray color, and as a result of analysis by a powder X-ray diffraction method, only a pyrochlore phase was recognized and it was assigned to Cd ₂ Sb ₂ O ₇ .

Comparative Example 1 An indium oxide powder (In ₂ O ₃ ) having a mean particle size of 1 μm or less and a purity of 99.99% and a soot oxide powder (SnO ₂ ) were mixed in a molar ratio of 0.9: 0.1. Weighed and wet ball mill mixed in ethanol solvent. Furthermore, after drying the obtained slurry at 60 ° C. for 24 hours, the resulting slurry was placed in an alumina crucible and
It was calcined at 000 ° C for 5 hours. The precursor after calcination was wet-ball milled again in an ethanol solvent, dried, and then 2% by weight of PVA was added as a molding binder.

Then, the particles are sized to 150 μm under, and 1
After uniaxial molding with a size of 5 mmφ × 3 mmt and rubber pressing (2 t / cm ² ), the molded green disk was baked at 1400 ° C. for 5 hours in the air.

The sintered body prepared as described above had a dark green color, and as a result of analysis by the powder X-ray diffraction method, only an indium oxide phase was recognized and attributed to In ₂ O ₃ . Further, no peak of tin oxide phase was observed and a shift was observed as compared with the peak of pure In ₂ O ₃ , so it was judged that the added tin oxide was replaced with indium oxide to form a solid solution.

As for the method of evaluating visible light transmittance in the present invention, since the sample is polycrystalline ceramics, the diffuse reflectance measuring method which is equivalent to the transmittance measuring was adopted. Here, as the measurement sample, the sinter prepared in the above example was crushed and uniaxially molded into a size of 25 mmφ × 3 mmt.

The standard white sample has a purity of 99.99.
% MgO powder molded by the same method as above was used. On the other hand, for the electrical conductivity measurement, a normal DC four-terminal method was employed, in which the sintered body prepared in the above example was cut into a rectangular parallelepiped with a diamond cutter and an element equipped with voltage and current electrodes was used.

Table 1 shows the diffuse reflectance measurement results of the oxides prepared in Examples and Comparative Examples of the present invention. As is clear from Table 1, the oxide of the present invention is a conventional material I
It can be seen that, as compared with TO (Comparative Example 1), the reflectance, that is, the visible light transmissivity is extremely high, and the absorption particularly on the short wavelength side of the visible region is significantly small.

[0038]

[Table 1]

Table 2 shows the electrical conductivity of the oxides prepared in the examples of the present invention at -40 ° C, room temperature (25 ° C) and 100 ° C. Here, it can be seen that the electric conductivity of each oxide is almost independent of temperature, is close to a metallic conductive behavior, and exhibits high electric conductivity.

[0040]

[Table 2]

[0041]

According to the present invention, the general formula: M _2-x Sb ₂
O ₇ [M = Zn, -0.2≤X≤0.2], and In, Ga, Al, Y, La, which are Group III metal elements containing a lanthanoid element in the complex oxide. Nd, S
a mixed oxide in which at least one selected from m, Eu, Gd, and Yb is doped at a rate of 0.01 to 20 atomic%,
All of the transparent conductive oxide materials, which are characterized by being double oxides having a pyrochlore type crystal structure, show high electric conductivity, but are more transparent than conventional materials, particularly in the visible short wavelength side. Of the material, and the material cost is reduced.

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Claims (3)

(57) [Claims] 1. Zn _2-x Sb ₂ O ₇ [-0.2 ≦ x ≦
0.2], which is a double oxide having a pyrochlore type crystal structure. 2. A group III metal element containing a lanthanoid element, such as In, Ga, Al, Y and La, at the Zn site,
2. The transparent conductive material according to claim 1, which is a complex oxide having a pyrochlore type crystal structure doped with at least one selected from Nd, Sm, Eu, Gd and Yb at a ratio of 0.01 to 20 atomic%. Oxide materials. 3. to generate oxygen vacancies by reduction atmosphere annealing, whereby a transparent conductive oxide according to claim 1 or 2, wherein it is a composite oxide having a pyrochlore-type crystal structure by injecting carrier electrons Material.